1. Field of the Invention
The present invention relates to hydraulic and pneumatic connectors, and more specifically to fluid connectors wherein a coupling nut or other fastener for a hydraulic tube is fixed to a base element so that it cannot back off due to vibration or other external forces.
2. Related Art
Fittings for providing a leak-proof attachment between a hydraulic or other fluid conducting tube and associated hardware such as actuators, manifolds, etc., are well known. Connectors and adapters may also serve the same function. One type of well known fitting is that shown in the Rosan, Sr. Patent, U.S. Pat. No. 3,702,707. A modified form of the Rosan fitting is shown in FIG. 1 herein and labeled as prior art.
The fitting combination 10 shown in FIG. 1 includes a fitting 12 threaded into a parent or base material 14. The parent material may be steel, aluminum or any other material forming the particular housing or hardware to which a fluid connection is to be made. For example, the parent material may be the wall of an actuator, manifold, etc. A cavity 16 defines a passageway 18 through which the fluid passes. The fluid may be hydraulic or pneumatic and may be under pressure. Pressures may be between 3,000 and 8,000 psi for example. The cavity 16 may be threaded with internal threads shown schematically at 20. The passageway may be threaded partially or entirely along its length. Mating threads on the fitting 12 engage the threads in the passageway.
The fitting forms a first primary seal 22 with the parent material 14. The first primary seal 22 is formed between a frusto-conical section in the parent material and a converging surface on the fitting 12. An elastomeric O-ring 24 serves as a secondary seal. The fitting includes serrations 26 extending in a direction parallel to the central axis 28 of the fitting combination and is held in engagement with the parent material 14 by a lockring 30. The lockring has internal serrations that mate with the external serrations 26 on the fitting and engages the parent material with external serrations 32 on its lower part and mating serrations formed in the parent material in a prebroached counterbore. The lockring 30 prevents rotation of the fitting relative to the parent material, thereby preventing the fitting from backing out of the parent material.
Upper serrations 34 formed in the upper portion of the lockring are used together with an appropriate tool to torque the fitting into the parent material.
A second primary seal 36 is formed between an upper frusto-conical section of the fitting 12 and a ferule or sleeve 38. The sleeve surrounds a portion of the end of a tube 40. A crimp 42 in the lower portion of the tube is partially formed during setting of the sleeve and is fully set when the sleeve 38 is cammed inward by the first frusto-conical portion of the fitting. The contact between the fitting, the sleeve and the tube forms the second primary seal.
The second primary seal is formed by torquing a B-nut 43 so that the threads 44 advance the B-nut downward over the fitting 12. Engagement of an angled surface on the inside of the B-nut with a correspondingly sloped flanged portion 46 extending outwardly from the sleeve causes the sleeve and tube to also move downward and into contact with the frusto-conical portion of the fitting.
The prior fitting combination is a multiple-piece arrangement and requires a series of steps to form a connection. The fitting must be threaded into the parent material and the lockring set into the prebroached parent material. Then, the tube, sleeve and B-nut are placed over the top of the fitting and tightened down. This provides a fitting with two primary seals, one between the fitting and the parent material and the other between the fitting and the sleeve. A secondary seal between the fitting and the parent material is provided with the O-ring. The fitting combination does not have a very low profile since the fitting extends substantially above the surface of the parent material and the B-nut is entirely exposed above the parent material. Furthermore, a lockwire is necessary to fix the B-nut relative to the fitting so that the B-nut does not back off the fitting due to external forces such as vibration. The lockwire can be passed through holes formed in the B-nut and secured to a boss on the parent material.
It is common practice to routinely replace the O-rings 24. This be done during an overhaul or cleaning of the hydraulic fittings. When this is done, the B-nut is loosened after removing the lockwire, and the tube and sleeve removed from the fitting. The fitting is then removed by lifting out the lockring with a lockring removal tool and unthreading the fitting. All parts are then cleaned and the O-ring replaced. If the tube, sleeve and B-nut only are to be removed, the fitting remains in the parent material. This may occur when the entire component is removed entirely from all hydraulic lines and serviced. During servicing, it is possible that the exposed fitting could be damaged. This could damage both the fitting and the parent material.
Similar characteristics are also present in other types of hydraulic fittings.
Use of a lockwire to fix the B-nut relative to the fitting is cumbersome and requires drilling a hole in one or more corners of the B-nut and finding a boss or tie-down location on the parent material to keep the B-nut from backing off. The lockwire is not a positive mechanical locking device and installation of lockwires may be subject to inconsistent installation techniques.
There is a need for an easy and reliable method and apparatus for positively locking the B-nut or other connector to the parent material or other base element which is fixed relative to the connector. Such an apparatus would provide a positive lock for maintaining the required leak-free fluid connection and provide a consistent method for locking the connector to the base element.